[runtime] We don't need an actual instance type for JSIteratorResult.

src/objects.cc

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/objects.h"
 
 #include <cmath>
 #include <iomanip>
 #include <sstream>
 
@@ skipping 13017 matching lines @@
     case JS_DATE_TYPE:
     case JS_ARRAY_TYPE:
     case JS_MESSAGE_OBJECT_TYPE:
     case JS_ARRAY_BUFFER_TYPE:
     case JS_TYPED_ARRAY_TYPE:
     case JS_DATA_VIEW_TYPE:
     case JS_SET_TYPE:
     case JS_MAP_TYPE:
     case JS_SET_ITERATOR_TYPE:
     case JS_MAP_ITERATOR_TYPE:
-    case JS_ITERATOR_RESULT_TYPE:
     case JS_WEAK_MAP_TYPE:
     case JS_WEAK_SET_TYPE:
     case JS_PROMISE_TYPE:
     case JS_REGEXP_TYPE:
     case JS_FUNCTION_TYPE:
       return true;
 
     case JS_BOUND_FUNCTION_TYPE:
     case JS_PROXY_TYPE:
     case JS_GLOBAL_PROXY_TYPE:
@@ skipping 6755 matching lines @@
   if (cell->value() != *new_value) {
     cell->set_value(*new_value);
     Isolate* isolate = cell->GetIsolate();
     cell->dependent_code()->DeoptimizeDependentCodeGroup(
         isolate, DependentCode::kPropertyCellChangedGroup);
   }
 }
 
 }  // namespace internal
 }  // namespace v8